SOS! Help! 400 Watt System with DIY LiFePo4 12v Battery

[solarnewb123]

Here's a quick diagram showing what Supervstech means by hooking up a 5v USB load to discharge a cell. (promoting Wills book too, getting brownie points)

I think I do need to buy the book.

 

[solarnewb123]

I think another reason why I'm confused is because I am not sure whether or not I need to use a BMS if I have the battery protect. I am using 3 schematics and not sure which one I should go off of, especially after watching the video I posted, here it is again:

What will my schematic ACTUALLY look like? can anyone tell me?

Other 3 schematics from Will's site attached.

 

[Freddmc]

This discussion is the exact reason I have decided to buy "drop ins" like Battle Born or Valente(or similar) As I watched some of Will's videos I thought "heck, I can order some cells from China and make my own battery". How difficult can it be. Add a few bus bars from negative to positive to negative, put it in an enclosure and VOILA, I just saved a $1000. Then I read about top balancing and bottom balancing and BMS's and low voltage cut-off and low temperature cutoff and discharge via USB and equalizing ,and- and- a whole host of other functions that come standard on a Battle Born. I have 300 watts of solar power on my motorhome that charge a couple of 100ah 12v batteries with an inverter and all the fuses and guages so I'm not entirely oblivious to this whole subject but it gets a little deeper than I want to go. Will does an absolute super job of explaining everything so much so that he sometimes makes it seem too easy.

 

[solarnewb123]

This discussion is the exact reason I have decided to buy "drop ins" like Battle Born or Valente(or similar) As I watched some of Will's videos I thought "heck, I can order some cells from China and make my own battery". How difficult can it be. Add a few bus bars from negative to positive to negative, put it in an enclosure and VOILA, I just saved a $1000. Then I read about top balancing and bottom balancing and BMS's and low voltage cut-off and low temperature cutoff and discharge via USB and equalizing ,and- and- a whole host of other functions that come standard on a Battle Born. I have 300 watts of solar power on my motorhome that charge a couple of 100ah 12v batteries with an inverter and all the fuses and guages so I'm not entirely oblivious to this whole subject but it gets a little deeper than I want to go. Will does an absolute super job of explaining everything so much so that he sometimes makes it seem too easy.

I appreciate your concern, but I think what Will (and staff/members) are doing is extremely helpful and invaluable, and I actually have learned quite a lot in the last few weeks about electrical engineering that was nothing but a blank slate to me until then. That being said, yes I agree somewhat with you, it's confusing as a beginner (especially with no prior knowledge whatsoever), but there is something to be said about learning how to design these systems yourself effectively (and safely) so that not only the initial cost of starting up is low, but also the cost to maintain it for a long time is low. This is why I am deciding to stick with learning the proper information and doing it on my own. On top of that, once I learn the information there is no unlearning it, so moving forward I will be able to save money and help others with their electrical systems. It's a win-win. I do agree that there could be some better strategies put in place for COMPLETE newbs like myself, but that's why the forum is here isn't it? And I can't believe how much I've been helped 1-on-1 already. The response rates are outstanding! Super pleased with this whole process, especially because my battery seems healthy and I'm proud of building it correctly and at a good price. I don't think the intention of Will's tutorials is to make them seem "too easy". Of course you're going to have to put in some work!

Nonetheless, I'm happy you've become satisfied with your set up! I think that's the goal here, isn't it?

Re: sorry again for all the questions, I'm just trying to learn! Thanks again for all your support

 

[Topmaike007]

If I want to run a blender for 1-2 minutes at a time, possibly every day or up to 4 times a week, would you recommend a different size inverter or stick with the 1000 watt? The alternative would be go higher, and get a 1500 watt inverter. In that case, would I also go with a larger battery protect? This would be nice in case I'd like to add solar panels in the future....right now I plan on using a 12v 400 watt solar panel system, but could add another one later with the larger inverter...what do you think?

The rest of my load will be roughly:

Computer=85w, 6 hours
Monitor Display=50w, 3 hours*
iPhone=18 watts, 7 hours
Portable Refrigerator=60w, 8 hours, 12v
Blender=600w, 2 minutes**
Lights=80w, 5 hours,12v
Sink Pump=60w, 1 hour, 12v
Roof Fan=50w, 4 hours, 12v


Thanks

Why not get light bulb that doesn't consume much power rather than that 80w you put up in your spec

 

[solarnewb123]

Why not get light bulb that doesn't consume much power rather than that 80w you put up in your spec

What do you suggest? Single-use battery powered lights or what?

 

[SCClockDr]

Convert your incandescent bulbs to LED's, I converted all our flouresant & incandescent fixtures to LED. It really helps with consumption.

 

[solarnewb123]

Ahhh, yes. I was calculating 8 LED lights at 10 watts per hour, for 5 hours. A bit high, I agree. I went high just because I wanted to make sure I was covering the max consumption when calculating so I didn't accidentally go to low.

 

[Night Owl]

yeah exactly. was using battery protect as a super large relay, but using individual cell monitoring to trigger it.

I just had time to watch that video and I don't blame you for being confused...as I am too! It seems the whole reason he needed to use the battery protect (and relay, and converter for the relay) was because the BMS he chose (1kw) was undersized for the load (the 2kw inverter). With a properly sized BMS for the load, the BMS itself could have been used as the battery protection...I think? That vid was a bit confusing.

So, with the Daly 200amp BMS, there would be no need for the relay in a 12v system powering a 1500 watt inverter, correct? My understanding is that a separate port BMS would be better but there has been some issue with the separate port sizes. So, would a 200amp common port work and eliminate a lot of the confusion around the relay and battery protect, as well as simplify the overall wiring for a 12v system running a 1500 watt inverter?

I have 2 REC N-Peak 315 watt panels in parallel for 630 watts 12v solar going to a victron 100/50 mppt smart charger with a 63amp breaker. This will charge 270Ah of lithium iron. I have eight 135Ah 3.2v cells arranged in 4 series of 2 parallel cells for one 12v 270Ah battery. So, one 200amp 4s 12v common port Daly BMS should be all I need if I understand everything correctly. Then wire in the fuse block and inverter with a 200amp fuse, but skip all of the relay and battery protect confusion. (Also have the victron smart temp sense on the battery and victron 712 monitor planned.)

 

[solarnewb123]

Hey so, what is the process for sizing your BMS anyway? Anyone?

 

[Supervstech]

Hey so, what is the process for sizing your BMS anyway? Anyone?

This is a good question.

I have read the inverter should be directly connected to the batteries...

I have read the BMS shouldn’t disconnect from the charge controller, as some CC’s will fail if PV is on, and battery is off...

 

[solarnewb123]

Isn't that why there is the need for a separate port BMS?